Thread: Oiling 3.5 heads on P76

Originally Posted by Hardchina

How much smaller are the chambers on the 3.5 heads? Would they bump the compression up a fair bit?

I believe the compression will be bumped up a bit, not sure how much but I am seriously considering an oil cooler to help keep the temp down. If anyone knows the figures I would like to know.

Originally Posted by Hardchina

How much smaller are the chambers on the 3.5 heads? Would they bump the compression up a fair bit?

The 4.4 heads were closely modelled on the 3.5 heads of the early 1970's. Having had quite a few off there is no significant difference that I could see. In the 80's the 3.5 heads gained slightly bigger valves. Most compression differences in production heads was done by piston dish volume. The 4.4 came in 9.0:1 car engine and 7.8:1 Terrier engine, the only difference was the machining of the piston crown. Using Rover 3.5 pistons in a P76 is a trap for young players, as the 20% extra stroke gives 20% more compression. So the ideal replacement piston for the 4.4 is the 8.13:1 Rover 3.5 piston, which will give about 9.5:1 in the 4.4